1. Field of the Invention
The present invention relates to a test chamber that can perform thermal and vibrational test on an object located within the chamber.
2. Description of Related Art
It is often desirable to test a component or assembly under simulated environmental conditions. For example, prototype electronic assemblies are exposed to various temperature, vibration and shock loads to determine whether the assembly can operate within its intended environment. Environmental testing is typically performed within a test chamber that is coupled to an ergonomic system which can vary the temperature and humidity within the cheer. The size of the test part can vary considerably, ranging from a large aircraft component to a small semiconductive device. The test chamber must be large enough to accommodate all types of test parts.
Using a large test chamber creates a relatively significant mass of air within the chamber. When temperature cycling a test part, the large air mass and inner chamber surfaces create a significant thermal inertia which must be overcome by the ergonomic system, resulting in additional work for the system and limiting the response time of the chamber. Some test chambers incorporate partition walls that reduce the volume of the test chamber. Assembling and disassembling the partition walls requires valuable testing time. It therefore would be desirable to provide an automated variable volume test chamber.
Thermal cycling a test part within a test chamber may result in a temperature differential between the test chamber and the room of more than 100.degree. C. A large temperature differential may cause the inner walls of the test chamber to expand or contract an amount different than the outer walls of the test chamber. In particular, if the inner chamber is at a sub-zero temperature the inner wall of the door will contract more than the outer wall of the door. It has been found that extreme thermal contractions/expansions of the inner wall will warp the door and break the seal between the chamber and the door. A thermal cycle of the door may also cause the door fasteners to fail. It would be desirable to have a test chamber door that will not warp or become damaged when subjected to thermal cycling.
After a part is tested, it is removed from the test chamber. It has been found that the operator may become injured or the test part may become damaged, if the test chamber is opened before the test is complete. For example, the operator may become burned if he enters the test chamber while at an elevated temperature. Likewise, opening the test chamber at a subzero temperature may result in condensation forming on, or within the test part and damaging the same. It would be desirable to provide a test chamber unit which does not allow the access door to be opened before the chamber reaches an operator "safe" condition. Additionally, it would also be desirable to allow an operator to open the access door from within the test chamber in the event the operator becomes locked in the chamber.
To apply vibration and shock loading, the test parts are typically mounted to a vibration table located within the test chamber. Because of the limited space of a test chamber, it can be difficult to mount the test part onto the table within the chamber. Therefore it would be desirable to provide a vibration table that can be pulled to a position outside of the test chamber.